Spectrum control problem for strongly irregular periodic vibrations of linear systems with zero mean of the coefficient matrix

We consider a linear periodic control system with zero mean of the coefficient matrix and with linear state feedback control periodic with the same period. We obtain necessary and sufficient conditions for the solvability of the frequency spectrum control problem with a given goal set for strongly irregular periodic vibrations. In this problem, one should find a feedback coefficient such that the closed system has a strongly irregular periodic solution with the desired frequencies.     

Economic design of a complete inspection plan with interactive quality improvement

Consider the monitoring of an ongoing production process subject to complete inspection. Inferior quality products are either reworked or scrapped to assure good outgoing quality. Whenever the quality characteristic of a product exceeds a predetermined action limit, remedial action is taken to restore the process to an in-control state. In addition, the decision maker has a learning opportunity to improve the process by investing in resources to identify and eliminate the causes of deviation from the target quality. Taking a learning action would improve the mean value of the quality characteristic of items produced in an out-of-control state. This paper proposes a cost model to determine the optimal number of learning actions to be taken and the optimal action limit. The model considers the trade-off between quality cost and process improvement cost.     

Multi-choice goal programming formulation based on the conic scalarizing function

The multi-choice goal programming allows the decision maker to set multi-choice aspiration levels for each goal to avoid underestimation of the decision. In this paper, we propose an alternative multi-choice goal programming formulation based on the conic scalarizing function with three contributions: (1) the alternative formulation allows the decision maker to set multi-choice aspiration levels for each goal to obtain an efficient solution in the global region, (2) the proposed formulation reduces auxiliary constraints and additional variables, and (3) the proposed model guarantees to obtain a properly efficient (in the sense of Benson) point. Finally, to demonstrate the usefulness of the proposed formulation, illustrative examples and test problems are included.     

A simulation-based test of stochastic multicriteria acceptability analysis using achievement functions

Stochastic multicriteria acceptability analysis using achievement functions (SMAA-A) is a preference model for discrete-choice decision making that inverts the traditional goal programming process by asking what combinations of aspirations are necessary to make each alternative the preferred one, rather than what alternative is preferred given a set of aspirations. In this paper, we test the ability of the model to discern good-performing alternatives from poorly-performing ones using a simulation study. Simulation results show that a suitably detailed construction of the acceptability index is particularly important, and that the resulting model can be fruitfully applied in the selection of a shortlist of alternatives from a larger set with only very limited decision maker involvement.     

Enhanced interactive satisficing method via alternative tolerance for fuzzy goal programming with progressive preference

This paper proposes an enhanced interactive satisficing method via alternative tolerance for fuzzy goal programming with progressive preference. The alternative tolerances of the fuzzy objectives with three types of fuzzy relations are used to model progressive preference of decision maker. In order to improve the dissatisficing objectives, the relaxed satisficing objectives are sacrificed by modifying their tolerant limits. By means of attainable reference point, the auxiliary programming is designed to generate the tolerances of the dissatisficing objectives for ensuring feasibility. Correspondingly, the membership functions are updated or the objective constraints are added. The Max–Min goal programming model (or the revised one) and the test model of the M-Pareto optimality are solved lexicographically. By our method, the dissatisficing objectives are improved iteratively till the preferred result is acquired. Illustrative examples show its power.     

Newsvendor-type models with decision-dependent uncertainty

Models for decision-making under uncertainty use probability distributions to represent variables whose values are unknown when the decisions are to be made. Often the distributions are estimated with observed data. Sometimes these variables depend on the decisions but the dependence is ignored in the decision maker??s model, that is, the decision maker models these variables as having an exogenous probability distribution independent of the decisions, whereas the probability distribution of the variables actually depend on the decisions. It has been shown in the context of revenue management problems that such modeling error can lead to systematic deterioration of decisions as the decision maker attempts to refine the estimates with observed data. Many questions remain to be addressed. Motivated by the revenue management, newsvendor, and a number of other problems, we consider a setting in which the optimal decision for the decision maker??s model is given by a particular quantile of the estimated distribution, and the empirical distribution is used as estimator. We give conditions under which the estimation and control process converges, and show that although in the limit the decision maker??s model appears to be consistent with the observed data, the modeling error can cause the limit decisions to be arbitrarily bad.     

网络传媒业供应链质量控制策略与组织模式选择

网络传媒供应链由内容制作商提供有价值的信息产品(如娱乐、资讯等)并通过网站提供给消费者.产品质量控制对网络传媒供应链至关重要.首先利用博弈论的方法分析内容制作商和网站分别独立决策时的策略,纳什均衡揭示双方的"搭便车"动机使供应链整体利润无法达到最优.然后利用最优化的方法分析他们在垂直整合模式下的策略,发现协调决策可以提高整体利润.最后考虑垂直整合模式的新增成本,分析需求质量弹性、利润分配均匀性和质量控制成本等因素对供应链是否采取垂直整合模式的影响.帮助理解网络媒体产业的质量控制策略和供应链组织模式.     

A Variance-Expected Compliance Model for Structural Optimization

The goal of this paper is to find robust structures for a given main load and its perturbations. In the first part, we show the mathematical formulation of an original variance-expected compliance model used for structural optimization. In the second part, we study the interest of this model on two 3D benchmark test cases and compare the obtained results with those given by an expected compliance model.     

基于目标规划和相对优势度的区间数互反判断矩阵排序法

针对决策信息以区间数互反判断矩阵形式给出的多目标决策问题.首先,给出了区间数一致性互反判断矩阵、相对优势度等概念.其次,建立一个目标规划模型,通过求解该模型得到区间数互反判断矩阵的权重向量,并利用各方案的相对优势度和进行方案的排序.提出了一种新的区间数互反判断矩阵排序方法,该方法具有操作简便和易于上机实现的特点.最后,通过实例说明方法的可行性和有效性.     

Numerical simulation of oblique and multidirectional wave propagation and breaking on steep slope based on FEM model of Boussinesq equations

Creating a representative numerical simulation of the propagation and breaking of waves along slopes is an important problem in engineering design. Most studies on wave breaking have focused on the propagation of normal incident waves on gentle slopes. In practice, however, waves on steep slopes are obliquely incident or multidirectional irregular waves. In this paper, the eddy viscosity term is introduced to the momentum equation of the improved Boussinesq equations to model wave dissipation caused by breaking and friction, and a numerical model based on an unstructured finite element method (FEM) is established based on the governing equations. It is applied to simulate wave propagation on a steep slope of 1:5. Parallel physical experiments are conducted for comparative analysis that considered a large number of cases, including those featuring of normal and oblique incident regular and irregular waves, and multidirectional waves. The heights of the incident wave increase for different periods to represent different kinds of waves breaking. Based on examination, the effectiveness and accuracy of the numerical model is verified through a comprehensive comparison between the numerical and the experimental results, including in terms of variation in wave height, wave spectrum, and nonlinear parameters. Satisfactory agreement between the numerical and experimental values shows that the proposed model is effective in representing the breaking of oblique incident regular waves, irregular waves, and multidirectional incident irregular waves. However, the initial threshold of the breaking parameter η_t^(I) takes different values for oblique and multidirectional waves. This needs to be paid attention when the breaking of waves is simulated using the Boussinesq equations.     

Fatigue crack growth under variable-amplitude loading: Part I – Model formulation in state-space setting

This two-part paper presents formulation and validation of a non-linear dynamical model of fatigue crack growth in ductile alloys under variable-amplitude loading including single-cycle overloads, irregular sequences, and random loads. The model is formulated in the state-space setting based on the crack closure concept and captures the effects of stress overload and reverse plastic flow. The state variables of the model are crack length and crack opening stress. This paper, which is the first part, presents formulation of the state-space model that can be restructured as an autoregressive moving average (ARMA) model for real-time applications such as health monitoring and life extending control. The second part is the companion paper that is dedicated to model validation with fatigue test data under different types of variable-amplitude and spectrum loading.     

桩基承台结构的波流力研究进展

我国近海风电场建设大多采用桩基承台结构．总结了不规则波浪和水流共同作用下桩基承台结构的波流力物理模型实验结果,得到了群桩效应系数及其变化规律,讨论了作用于近水面承台底部的波浪拍击力;从理论上分析了规则波作用下承台对桩基波浪力的影响;建立了规则波与桩基承台相互作用的数值模型,揭示了波浪在承台的上浪与爬高及其水动力特征．鉴于桩基承台结构包含多个斜桩和较大尺度的承台,在波浪与水流作用下该结构物附近的流场结构十分复杂,有必要针对结构附近的流动结构以及自由表面大变形开展细致的实验和数值模拟研究,以进一步揭示作用于这类结构的波流力变化规律及其机理.     

Chaotic vibrations in nonlinear problems of bar structures

In the response of nonlinear mathematical models which describe vibrations of structural elements one could observe an irregular behaviour which is called chaos. Loss of the information on initial states in deterministic dynamical systems after a short time of theirs evolution, increasing amplitudes of displacements, velocities and accelerations, sensitive dependency on initial conditions makes chaos dangerous phenomenon in mechanics of construction. In this article quantitative (bifurcation diagrams, Poincare sections and Fourier power spectrum analysis) identication methods of the chaotic dynamics in geometrically nonlinear model of one DOF Mises truss are shown. Main goal of this article is to show and verify dangerous influence of chaos (in the engineering sense) on the analyzed structure. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

The DWT power spectrum analysis of the large scale structure in the universe : Method and simulation tests

Based on the discrete wavelet transformation ( DWT), we present a pixelized method of estimating the power spectra of galaxy samples. With local properties of wavelet both in physical and wavenumber spaces, DWT power spectrum is equal to the corresponding band average of Fourier power spectrum. The DWT estimator is optimized in the sense that the spatial resolution is adaptive automatically to the perturbation wavelength to be studied. Under the assumption of ergodicity, the spatial average of local DWT fluctuation modes provides a fair estimation of the ensemble average. We test DWT spectra of four typical cold dark matter (CDM) structure formation models with numerical simulations. To consider the infections of various observation effects to the DWT spectra, we introduce irregular survey geometries, a given sampling rate, radial selection effects and redshift distortion effects into our mock samples. The numerical results show that, owing to its local properties, DWT spectrum is less affected by the sampling rate, survey geometry, and statistical ensemble fluctuations. With fast wavelet decomposition algorithm, DWT can be used to analyze large survey samples, which is of direct significance in precise measurement of the cosmological parameters from the galaxy redshift surveys of next generation.     

Wave propagation analysis in high-speed railway catenary system subjected to a moving pantograph

An analytical model is used to study the wave propagation property in the high-speed railway catenary system subjected to a moving pantograph. The contact and messenger wires are modelling by tensioned cables. The Fourier transform is exploited to find out the solution of the governing equation of the tensioned cable, whose vertical deflection is assumed as the superposition of two waves propagating to opposite sides. Through applying the boundary conditions of a real railway catenary system, the wave propagation model of the catenary system is constructed. The effect of the messenger/contact wire tensions on the wave reflection and transmission at the dropper point is analysed. On the basis of a complete model subjected to a moving load, the wave propagation behaviour in the contact wire is analysed. The results demonstrate that several groups of dominant wave frequencies can be observed from the forward and backward waves under the excitation of a constant moving load. Two significant wave components are introduced by a time-varying moving load due to the Doppler Effect. The effect of the matching between the dominant wave frequencies and the natural frequencies sensitive to the moving load on the contact quality is investigated in combination with a realistic FEM pantograph-catenary model. The results show that the resonance may occur when the dominant wave frequency is consistent to the natural frequency sensitive to the moving load, which can be used to reveal the effect of operation and structural parameters on the current collection quality of a pantograph-catenary system.     

Modelling of extreme wave heights and periods through copulas

Optimal design of coastal or offshore structures requires the estimation of extreme quantiles of oceanographic data such as wave heights and wave periods. Since there are strong correlations between oceanographic variables, it is necessary to use multivariate models in order to capture its dependencies. To achieve this, an approach based on copulas is proposed and is compared to a model based on the physical behaviour of waves.     

Robust spectral risk optimization when the subjective risk aversion is ambiguous: a moment-type approach

Choice of a risk measure for quantifying risk of an investment portfolio depends on the decision maker’s risk preference. In this paper, we consider the case when such a preference can be described by a law invariant coherent risk measure but the choice of a specific risk measure is ambiguous. We propose a robust spectral risk approach to address such ambiguity. Differing from Wang and Xu (SIAM J Optim 30(4):3198–3229, 2020), the new robust model allows one to elicit the decision maker’s risk preference through pairwise comparisons and use the elicited preference information to construct an ambiguity set of risk spectra. The robust spectral risk measure (RSRM) is based on the worst case risk spectrum from the set. To calculate RSRM and solve the associated optimal decision making problem, we use a technique from Acerbi and Simonetti (Portfolio optimization with spectral measures of risk. Working paper, 2002) to develop a new computational approach which is independent of order statistics and reformulate the robust spectral risk optimization problem as a single deterministic convex programming problem when the risk spectra in the ambiguity set are step-like. Moreover, we propose an approximation scheme when the risk spectra are not step-like and derive a bound for the model approximation error and its propagation to the optimal decision making problems. Some preliminary numerical test results are reported about the performance of the robust model and the computational scheme.

     

Wavelet analysis of cycle-to-cycle pressure variations in an internal combustion engine

Using a continuous wavelet transform we have analyzed the cycle-to-cycle variations of pressure in an internal combustion engine. The time series of maximum pressure variations are examined for different loading and their wavelet power spectrum is calculated for each load. From the wavelet power spectrum we detected the presence of long, intermediate and short-term periodicities in the pressure signal. It is found that depending on the load, the long and intermediate-term periodicities may span several cycles, whereas the short-period oscillations tend to appear intermittently. Knowledge of these periodicities may be useful to develop effective control strategies for efficient combustion.     

基于失效情景的应急设施选址问题

非常规突发事件巨大的破坏力以及发生时间、地点和规模的不确定性,使应急系统内设施有可能被破坏而失效,因此选址时必须考虑设施失效情景的发生.给出以最大限度覆盖用户需求为目标,基于失效设施数目具有不确定性情景的设施选址双层随机规划模型;通过计算模型上下界,给出减小规模的等价模型,降低了双层规划求解难度;最后实验验证了模型的合理性,并给出新增选址方案.     

用CT-VOF法在数值波试验槽中生成线性和非线性波

为渡水槽中波的模拟和传播提出了二维的数值模型．假设流动的流体为粘性、不可压缩的,并将Navier-Stokes方程和连续性方程作为控制方程．用标准的k-ε模型来模拟紊流流动;用交错网格的有限差分法,离散化Navier-Stokes方程;并用简化的标识和单元(SMAC)方法进行求解．使用活塞型波发生器生成并传播波;数值渡水槽的端部采用敞开式的边界条件．为了证明模型的有效性,进行了一些标准的试验,如顶盖驱动的方腔测试试验、单向的常速度场试验以及干燥河床上的溃坝试验．为了论证方法的性能及其精度,将所生成波的结果与已有波理论的结果进行比较．最后,采用群集技术(CT)生成网格,并提出最佳的网格生成条件．